This invention relates to arrangements for ascertaining the directivity of transient disturbances appearing on power lines and, more particularly, to arrangements for recording data concerning the appearance of the more significant disturbances and ignoring disturbances of lesser magnitude or energy content.
Heretofore, it has been known, as for example, from the study of K. T. Huang reported in Department of Defense Report No. TN-1327 entitled "Power Line Transient Source and Direction of Propagation Detector" published in February 1974 that the direction of the location of the source of a transient signal creating a disturbance on an electrical power system can be ascertained by determining the polarity of the transient current and voltage. This relationship holds true provided that the respective polarities are determined within a short time of the occurrence of the transient. It was Huang's hypothesis that at the moment when the distance occurs the transient current and voltage are in phase and that if a sensor can pick up information on the polarity of the transient voltage and the direction of transient current at that critical moment, the direction of the transient along the lines of the power system can be determined. The source of the transient could then be located by tracing along the power line in the ascertained direction. Instruments have for some time been commercially available that attempt to indicate the direction of transient disturbances. Experience with such equipment has, however, not been wholly satisfactory, it sometimes not being possible to indicate the direction of a transient's source and at other times, it has been suspected that the wrong direction has been indicated.
Equipment for reliably indicating other parameters of line voltage disturbances has, however, heretofore been made widely available. For example, it has for some time been practical to monitor 60 Hz mains and to record the time of occurrence and the peak value of a transient impulse, the number of cycles of the mains frequency during which a line voltage sag or surge persisted, and the slow-averaged RMS level of the line voltage. Instruments are available which have the ability to store data concerning a limited number of transients that may occur while the outprinting equipment is operating, and when the capacity of this temporary memory is exceeded, to printout a summary count of the number of excess transients and of the highest amplitude reached by any of the excess transient disturbances. The Dranetz Engineering Laboratories' Model 606 "Power-Line Disturbance Analyzer" is an example of such presently available equipment.
While it would be of obvious advantage to combine the features of the foregoingly described two types of equipment, the combination is not warranted unless the reliability of the direction-indicating technique can be improved.